The objective of this study is to determine the mechanisms by which genes specify the connectivity of nerve cells. The first stage of this research is to study mutants which have altered neural networks and determine the physiological and morphological effects of these mutations. We will work with normals and mutants of the flight control system of Drosophila. The flight neurons in the thoracic ganglion are amenable to anatomic, genetic, and electrophysiologic investigation. For anatomic analysis, we will cut a complete set of EM serial sections through the ganglion. Using the computer aided system of Levinthal and co-workers, we will make a three dimensional reconstruction of the relevant parts of the nervous system. In this type of complete reconstruction, the number and area of synapses between any two cells are determined and provide a quantitative measure of the strength of the synapse. There are 26 neurons controlling the power muscles of flight. We have developed electrophysiological techniques to record the output of each cell during flight, to stimulate each cell, and to determine the inter-connections between cells which are responsible for their coordinated activity. We will analyze an isogenic, hmozygous wild type strain, the mutant stripe, and nine other winged but flightless mutants. We hope to determine the effect of each of these mutations on the nervous system.